bridge: Do not add bridges with '/' in name.

bridge: Do not add bridges with '/' in name.

This effectively stops vswitchd from creating bridges with '/' in the
name. OVS used to print a warning but the bridge was created anyway.

This restriction is implemented because the bridge name is part of a
filesystem path.

This check is no substitute for Mandatory Access Control, but it
certainly helps to catch the error early.

Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com>
[blp@ovn.org added a test]
Acked-by: Ben Pfaff <blp@ovn.org>